A wheelset is a pair of railroad vehicle

wheels A wheel is a circular component that is intended to rotate on an axle bearing. The wheel is one of the key components of the wheel and axle which is one of the six simple machines. Wheels, in conjunction with axles, allow heavy objects to b ...

mounted rigidly on an

axle An axle or axletree is a central shaft for a rotating wheel or gear. On wheeled vehicles, the axle may be fixed to the wheels, rotating with them, or fixed to the vehicle, with the wheels rotating around the axle. In the former case, beari ...

such that both wheels rotate in unison. Wheelsets are often mounted in a bogie ("truck" in

North America North America is a continent in the Northern Hemisphere and almost entirely within the Western Hemisphere. It is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South America and th ...

) – a pivoted frame assembly holding at least two wheelsets – at each end of the vehicle. Most modern freight cars and

passenger cars A car or automobile is a motor vehicle with wheels. Most definitions of ''cars'' say that they run primarily on roads, seat one to eight people, have four wheels, and mainly transport people instead of goods. The year 1886 is regarded as t ...

have bogies each with two wheelsets, but three wheelsets (or more) are used in bogies of freight cars that carry heavy loads, and three-wheelset bogies are under some passenger cars. Four-wheeled goods wagons that were once near-universal in

Europe Europe is a large peninsula conventionally considered a continent in its own right because of its great physical size and the weight of its history and traditions. Europe is also considered a Continent#Subcontinents, subcontinent of Eurasia ...

and

Great Britain Great Britain is an island in the North Atlantic Ocean off the northwest coast of continental Europe. With an area of , it is the largest of the British Isles, the largest European island and the ninth-largest island in the world. It ...

and their colonies have only two wheelsets; in recent decades such vehicles have become less common as trainloads have become heavier.

Conical wheel-tread

Most train wheels have a conical taper of about 1 in 20 to enable the wheelset to follow curves with less chance of the wheel

flange A flange is a protruded ridge, lip or rim (wheel), rim, either external or internal, that serves to increase shear strength, strength (as the flange of an iron beam (structure), beam such as an I-beam or a T-beam); for easy attachment/transfer of ...

s coming in contact with the rail sides, and to reduce curve resistance. The rails generally slant inwards at 1 in 40, a lesser angle than the wheel cone. Without the conical shape, a wheel would tend to continue in a straight path due to the inertia of the rail vehicle, causing the wheelset to move towards the outer rail on the curve. The cone increases the effective diameter of the wheel as it moves towards the outer rail, and since the wheels are mounted rigidly on the axle, the outer wheels travel slightly farther, causing the wheelsets to more efficiently follow the curve. Abnormal wear at the wheel–rail interface is thus avoided, along with the loud, piercing, very high-pitched squeal which usually results from it – especially evident on curves in tunnels, stations and elevated track, due to flat surfaces slipping and flanges grinding along the rail. However, if the degree of conicality is inappropriate for the suspension and track, an unpleasant

oscillation Oscillation is the repetitive or periodic variation, typically in time, of some measure about a central value (often a point of equilibrium) or between two or more different states. Familiar examples of oscillation include a swinging pendul ...

can occur at high speeds. Recent research is also showing that marginal changes to wheel and rail profiles can improve performance further. Not all railroads have employed conical-tread wheels. The Bay Area Rapid Transit (BART) system in

San Francisco San Francisco (; Spanish for " Saint Francis"), officially the City and County of San Francisco, is the commercial, financial, and cultural center of Northern California. The city proper is the fourth most populous in California and 17t ...

, built with cylindrical wheels and flat-topped rails, started to re-profile the wheels in 2016 with conical treads after years of complaints about the squeal by its passengers. Australia's

Queensland Railways Queensland Rail (QR) is a railway operator in Queensland, Australia. Owned by the Queensland Government, it operates local and long-distance passenger services, as well as owning and maintaining approximately 6,600 kilometres of track and relat ...

used cylindrical wheels and vertical rails until the mid-1980s, when considerably higher train loads made the practice untenable.

Specialised wheelsets

Some rubber-tyred metros feature special wheelsets with

rubber Rubber, also called India rubber, latex, Amazonian rubber, ''caucho'', or ''caoutchouc'', as initially produced, consists of polymers of the organic compound isoprene, with minor impurities of other organic compounds. Thailand, Malaysia, and ...

tyres outside of deep-flanged steel wheels, which guide the bogie through standard railroad switches and keep the train from derailing if a tyre deflates. The

system A system is a group of interacting or interrelated elements that act according to a set of rules to form a unified whole. A system, surrounded and influenced by its environment, is described by its boundaries, structure and purpose and express ...

was originally conceived by Michelin for the Paris Métro; the first line opened in 1956.

Gallery

File:Denney Axle.jpg,

Denney axle Denney may refer to: * Denney, Territoire de Belfort Denney () is a commune in the Territoire de Belfort department in Bourgogne-Franche-Comté in northeastern France. See also *Communes of the Territoire de Belfort department The followin ...

File:Rollingstock axle.jpg, Railroad car wheels are rigidly mounted on an axle to rotate in unison File:SBB Cargo Güterwagen Radsätze.jpg, Swiss Federal Railways wheelsets with fitted journals File:Rail_axl_at_Texas_Transportation_museum.JPG, Wheelset from a railroad speeder; the wheels are pressed steel and the flanges are smaller than those of full-sized rail vehicles File:GWR Spoked wagon wheels.jpg, A wheelset from a Great Western Railway wagon, showing a plain bearing end File:Bettendorf truck at Illinois Railway Museum.JPG, A freight bogie of the Bettendorf pattern, which became standard in North America and elsewhere File:Пам.Энгельса29 КП Метро Штангист в каске.JPG, Wheelset as part of a welded sculpture in

Kharkiv Kharkiv ( uk, Ха́рків, ), also known as Kharkov (russian: Харькoв, ), is the second-largest city and municipality in Ukraine.

File:Heidelberg funicular wheelset.jpg, Wheelset of a two-rail

funicular A funicular (, , ) is a type of cable railway system that connects points along a railway track laid on a steep slope. The system is characterized by two counterbalanced carriages (also called cars or trains) permanently attached to opposite ...

File:Muzeum MHD, dvoukolí vozu petřínské lanovky 1891.jpg, Funicular wheelset with Abt

rack and pinion brake Rack or racks may refer to: Storage and installation * Amp rack, short for amplifier rack, a piece of furniture in which amplifiers are mounted * Bicycle rack, a frame for storing bicycles when not in use * Bustle rack, a type of storage bin ...

References

External links

*
Train wheels
{{Authority control Bogie

Conical wheel-tread

Specialised wheelsets

Gallery

See also

References

Further reading

External links